Matthew's impacts are already being felt in the Caribbean and the powerful category 4 hurricane is expected to bring life-threatening conditions as it passes closer to Haiti, Cuba and Jamaica through Tuesday.

Outer portions of the storm were already bringing strong winds and heavy rains to much of Hispaniola, including Haiti and Jamaica as of Monday evening, according to AccuWeather Meterologist Alyson Hoegg.

In poverty-stricken Haiti, where many residents live in slums close to the sea, the effects could be devastating. Reuters reported that many residents in the coastal city of Les Cayes, in homes just feet from the ocean, were refusing to evacuate. Many are hesitant to leave because they are fearful their belongings will be stolen.

A police officer helps residents climb down from a pickup after being evacuated prior the arrival of Hurricane Matthew, in Tabarre, Haiti, Monday, Oct. 3, 2016. (AP Photo/Dieu Nalio Chery)

According to Reuters, the mayor of the Haiti's largest slum, Cite Soleil located in the capital of Port-au-Prince, requested that the government help transport 150,000 people whose homes were threatened.

"Those people are living all along the seashore in a bunch of huts which usually can't even really protect them from ordinary rain. Now we are talking about a strong hurricane. Imagine the disaster we may have to face here," Mayor Frederic Hislain told Reuters.

Global aid organizations, CARE, the Red Cross and Mercy Corps, said they were closely monitoring the path of the storm as it nears Haiti and had already begun initiating response efforts.

"Based on our experience we anticipate the most pressing needs to be clean drinking water and shelter," Jessica Pearl, Haiti country director for Mercy Corps said in a statement. "Haiti is not well-prepared for a major hurricane, and we are particularly concerned about people living in rural areas who are unlikely to be receiving preparedness or evacuation information."

CARE said it was coordinating with the government to help people prepare and evacuate from areas where extreme storm surges are forecast. The organization has already begun distributing supplies such as clean drinking water, tarps, blankets and hygiene kits along to the southern peninsula of Haiti, where access is expected to be difficult following the storm.

Hoegg said the worst storm surge will be over the southern portion of the Tiberion Peninsula, where 10-15 feet of storm surge is expected.

"Hurricane Matthew could have devastating impacts in Haiti, as the country has not experienced a storm of this magnitude since 1954. The people of Haiti were already suffering from a drought as a result of El Niño and now they will likely endure the shock of torrential flooding as a result of this storm," said Jean-Michel Vigreux, CARE country director in Haiti. "With the amount of rain expected, thousands are vulnerable to extreme flooding and mudslides due to deforestation in Haiti. The earlier people can get to shelters, the better, which is what we are emphasizing now,"

The government of Haiti said that more than 18,000 volunteers are on alert and ready to assist populations and support humanitarian workers.

At least one person has already died in Haiti as a result of Matthew, according to the Associated Press. Two fishermen were thrown overboard when their boat overturned in rough seas off the coast of Saint Jean du Sud, a fishing town located on the southwestern tip of the country. The body of one of the fishermen was recovered Monday, while the other person is still considered missing.

People take cover from the rain with a piece of cardboard as they ride on the bed of a pickup truck in Tabarre, Haiti, Monday Oct. 3, 2016 (AP Photo/Dieu Nalio Chery)

In Jamaica, reports of flooding have already come in from around the island, according to Evon Thompson, the head of Meteorological Service of Jamaica.

Jamaica's parliament will be postponed on Tuesday, while the National Emergency Operations Centre (NEOC) said that all ministries, departments and agencies will be closed until after the passage of Matthew. Essential services will remain open and ready to respond, the NEOC said.

Desmond McKenzie, Jamaica's minister of local government and community development, said that there are 89 active shelters accommodating 1,845 people who evacuated their homes.

The Cuban News Agency reported that 180,000 Cubans will have to move to schools and government facilities for shelter since they live in areas that could be overrun by flooding and landslides.